The Taliban have released a video they claim shows fighters preparing for the attack on Camp Bastion which earlier this month destroyed aircraft and equipment worth more than £100 million.

The video shows young men in American military clothing practicing breaching a wire fence and being briefed on the position of aircraft inside the sprawling Helmand base.

Fifteen fighters armed with rocket-propelled grenades and assault rifles attacked the airfield beside the camp, where Prince Harry is deployed, on September 14.

Two United States Marines were killed and six American Harrier aircraft were destroyed and two others badly damaged.

All but one attacker was killed as gunners from the RAF Regiment and American marines fought the insurgents in a fire fight lasting nearly five hours.

The propaganda film, which was emailed to Afghan journalists by a Taliban spokesman, shows young men wearing American Army fatigues practicing cutting a hole in a wire fence and charging through the breach.

One of the fighters then lists reasons, in English, why he and his comrades are prepared to die in the attack, complaining the West and coalition have insulted Islam, the Prophet Mohammed and the Koran.

Hours after the attack, the Taliban released a statement saying it had been in retaliation for an American-made anti-Islam film which has caused protest across the Muslim world.

The final scene shows a man pointing to a crude map drawn on a white board, showing the positions of helicopters, planes and hangars.

It was not possible to verify the authenticity of the footage and nothing in the video indicated when, or where, it was filmed. A spokesman for British forces in Helmand said they did not comment on insurgent propaganda.

The Nato coalition has already confirmed the attackers wore American uniform and split into three teams which appeared "well equipped, trained and rehearsed".

The American military on Monday also released more information on the assault, with marines describing how they fought to save their aircraft and repel the attack.

American marines on the airfield believed the first explosions, when insurgents attacked at around 10pm, could be controlled detonations outside the wire.

"I started hearing explosions, so I went outside to see what was going on," said Staff Sgt Justin Pauley.

"I saw a rocket-propelled grenade flying overhead, and I immediately told my marines to get their [equipment] on."

Lt Col Stephen Lightfoot, commander of a marine attack helicopter squadron, said: "I went outside after hearing the first explosion and within 15 seconds I heard another explosion.

"That's when I saw the flames on the Harrier flight line. I yelled out for everyone to get to the bunkers on our compound."

As British and American troops moved to fight the attackers, the marines also tried to scramble as many of their aircraft as possible to prevent more being damaged on the ground.

Once in the air, their attack helicopters also opened fire on the insurgents.

Lt Col Lightfoot said: "It was a very dark night. There was no moon. However, on the flight line there were multiple aircraft on fire and a couple other areas were on fire as well, so it was extremely bright. There were 50 to 100 foot flames and a lot of thick smoke."

Six AV-8B Harrier jets were destroyed and two more were significantly damaged. Each is estimated to cost around £20 million. Several buildings and refuelling points were also damaged.

Meanwhile, the coalition said insurgent attacks decreased nine per cent in August, compared with the last year – continuing a fall-off that started in July after a spike in attacks in May and June.